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    <title>Document</title>
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    <script>
      //编写一个函数，接受一个数组作为参数，并返回数组中所有奇数的平均值（如果没有奇数则返回0）
      let arr = [4, 6, 10, 20, 2, 1, 3, 5, 7, 9]
      function average(a) {
        let newArr = []
        let sum = 0
        for (let i = 0; i < a.length; i++) {
          if (a[i] % 2 !== 0) {
            newArr.push(a[i])
            sum += a[i]
          }
        }
        if (newArr.length === 0) return 0
        else {
          return sum / newArr.length
        }
      }

      console.log(average(arr))
    </script>
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